1. Field of Invention
The invention relates to a display system and a light tunnel thereof, and, in particular, to a projection system and a light tunnel thereof.
2. Related Art
Due to demands for large display area and compact, light-weight systems, image projection systems have now become one of the most popular products in the opto-electronic industry.
Referring to FIG. 1, an image projection system, hereinafter referred to as a projection system 1, has a light source 10, a color wheel assembly 11, a light tunnel 12, a lens assembly 13, a digital micro-mirror device (DMD) 14 and a projecting unit 15. The light source 10 emits light to the color wheel assembly 11 and then into the light tunnel 12. Then, the lens assembly 13 focuses the light onto the DMD 14. Driving electrodes are provided to control tilt angles and deflection times of micro mirrors (not shown) on the DMD 14 to switch reflection directions of the light, and then the light is projected onto a screen 16 through the projecting unit 15 for imaging.
Referring to FIGS. 1 and 2, the conventional light tunnel 12 is mainly composed of four optical elements 121, which are assembled using a jig to fix the four optical elements 121. Then, an adhesive 122 is applied to all the junctions between adjacent pairs of optical elements 121 so that the optical elements 121 can be combined together. Because inner surfaces of the light tunnel 12 have reflective layers, the light emitted from the light source 10 enters the light tunnel 12 through an inlet 123, then is reflected by the reflective layers many times, and then is outputted from an outlet 124 so that the luminance of the light becomes uniform.
However, because a space for the adhesive 122 has to be left between the optical elements 121, a contact surface S between the optical elements 121 is smaller, as shown in FIG. 2. When an external force is applied to the light tunnel 12, the optical elements 121 may be separated due to insufficient structural integrity so that the efficiency of the light tunnel 12 is adversely influenced. In addition, because the temperature of the light emitted from the light source 10 is very high, the environmental temperature is elevated such that the adhesive 122 of the light tunnel 12 adjacent to the light source 10 tends to become brittle. Similarly, the structural intensity between the optical elements 121 of the light tunnel 12 is insufficient and the optical elements 121 tend to separate from one another.